Shell-and-Tube Heat Exchanger

Abstract

A shell-and-tube heat exchanger for the treatment of juices and juice-type foodstuff products with medium to high viscosity, with at least one jacket tube containing at least one inner tube, whereby the inner tube and / or the jacket tube is or are formed as a swirl tube with multi-start spirals running like a thread at an angle to the tube axis, a crossed and twisted tube with crossing spirals at least essentially symmetrical to the tube axis, each with an angle of incidence between 67° and 72° to the tube axis, i.e. with an angle of twist of 23° to 18° to the tube axis, is used as an inner and / or outer tube. The spiral depth is about 0.8 mm to 1.2 mm.

Description

CROSS-REFERENCE TO RELATED APPLICATION[0001]The present application claims the benefit of priority of German Application No. 102009040558.5, filed Sep. 8, 2009. The entire text of the priority application is incorporated herein by reference in its entirety.FIELD OF THE DISCLOSURE[0002]The disclosure relates to a shell-and-tube heat exchanger of the type used in beverage bottling operations with juices and juice-type foods, and an inner and / or jacket tube of a shell-and-tube heat exchanger of this type.BACKGROUND[0003]A shell-and-tube heat exchanger for the treatment of juices with fibers and / or particles in which simply twisted inner and / or outer tubes are used is known from DE 600 19 635 T2. In the inner tube the angle of twist is shown at approximately 45°, whereas the angle of twist in the jacket tube is illustrated with about 75°, referred to the tube axis in each case. With this shell-and-tube heat exchanger a disadvantage is that to increase the heat transfer very substantial ...

AI Technical Summary

Benefits of technology

[0005]An aspect of the disclosure is to provide a shell-and-tube heat exchanger of the type mentioned in the introduction as well as a jacket tube and / or inner tube for a shell-and-tube heat exchanger of this nature, which, when processing particularly juices or juice-type foodstuff products with low, medium or high viscosity, facilitates optimally short dwell times and small heat exchange surfaces despite only moderate feed pressure. This applies to all liquid foodstuffs in this viscosity range.

[0006]Through the use of at least one crossed and twisted tube in the shell-and-tube heat exchanger (for the jacket tube and / or each inner tube) a substantial increase in the heat transfer is achieved due to the crossing spirals. However, with the increase of the pressure loss associated with the cross-twisting, the achievable increase in the heat transfer is brought to an optimum relationship in the through-flow by restricting the angle of incidence α to 72° to 67° longitudinally to the tube axis and the resulting angle of twist of 18° to 23° perpendicular to the tube axis, i.e. to a relatively acute angle, which, despite only moderate feed pressure, results in a smaller heat exchange surface. In other words, due to the use of crossed and twisted tubes of this nature, the shell-and-tube heat exchanger needs a relatively small heat exchange surface and therefore a short conveying distance. With juices and juice-type foodstuff products the tendency to form product deposits is of secondary importance, because with the use of crossed and twisted tubes with the stated flat angles of twist the primary factor is that pulp, fibers or particles as constituents of juices or juice-type foodstuff products do not tend to cling and collect due to the flat angle of twist, but are instead rapidly flushed further. Moreover, in this way cleaning to a hygienically flawless condition is possible.

[0008]In an expedient embodiment the width in the indentation, viewed in the direction of the tube axis, is a multiple of the spiral depth. It should be between about 5.0 and 20.0 mm. The indentations are relatively wide cavities, on their adjacent ribs of which constituent parts of the product are rapidly flushed further and which also facilitate hygienically flawless cleaning, e.g. for a change of product.

Problems solved by technology

With this shell-and-tube heat exchanger a disadvantage is that to increase the heat transfer very substantial pressure loss is accepted for a constant area presented to the flow and the boundary layer of the flow is induced to strong rotation at the spirals which run with the same angle of twist to the tube axis.

This requires very high feed pressure, which may be disadvantageous for the product, for the treatment of the product in the shell-and-tube heat exchanger.

An angle of twist of 45° is also mentioned, which is regarded as optimum for the heat transfer, but which however leads to an inadmissible heavy formation of deposits with milk and milk products.

Angles of incidence between 25° and 35° and the additional surface treatment are consequently optimum for milk and milk products with regard to the inhibition of the product-specific formation of deposits, but, as with the current angle of 45° to the tube axis, they give an unfavorable relationship between the increase in the heat transfer obtained and an excessive increase in the loss of pressure in the flow.

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